Most high pressure reservoirs are provided with pressure limiting valve in order to ensure that pressure inside the reservoir does not exceed a predetermined pressure threshold. The high pressure reservoir of a direct fuel injection equipment is a so commonly called “common rail” and is generally an elongated tubular member having a thick wall with a high pressure inlet, for the fuel to get in the rail and, a plurality of outlets for delivering fuel to injectors. The rail is further provided with a pressure relief orifice extending through a portion of the wall of the rail, the opening and closing of the orifice being controlled by a pressure limiting valve.
The valve is a standalone mechanical equipment and, the pressure threshold at which a closing member moves from a closed position to an open position is set by the force of a biasing spring so, when the pressure in the rail reaches the threshold, the opening force generated by the fuel on the closing member exceeds the opposed closing force of the biasing spring. The member is pushed in the open position and fuel is enabled to exit the rail via the relief orifice then to flow out via a low pressure outlet.
The valve is, as standalone equipment, the housing of the valve is fixedly arranged on the rail obliging to complementary geometries on both the rail and valve. Such obligation increases technical complexity and associated cost. Furthermore, the adjustment parameters for tuning the pressure threshold are set on a small batch of valves then, the setting is reproduced on all valves, which are individually checked. The statistic distribution of actual pressure threshold over the entire production of valves has distribution tails with rejected valves which individual threshold are out of specification.